Weathering of sulphide minerals and trace element speciation in tailings of various ages in the Guanajuato mining district, Mexico
Weathering of sulphide minerals and trace element speciation in tailings of various ages in the Guanajuato mining district, Mexico
复制标题
DOI：
10.1016/j.catena.2007.03.014
复制
发表时间：
2007-12
期刊：
影响因子：
6.2
通讯作者：
Y. Arroyo;C. Siebe
中科院分区：
文献类型：
--
作者：
Y. Arroyo;C. Siebe
研究了墨西哥瓜纳华托矿区不同年龄尾矿中与硫化物矿物伴生的痕量元素As、Cu、Pb、Zn的行为。目的是确定随着尾矿年龄的增长，TE进入的主要组分，并确定主要金属组分达到平衡需要多长时间。采集了不同年限(0、2、4、16、70、75和100年)的矿山废弃层地表样品21个，测定了它们的王水可提取态砷、铜、铅、锌的含量。我们还应用了顺序提取程序来定量水溶性TE以及与碳酸盐、氧化铁、硫化物和残余物相关的TE。用X射线衍射仪对样品进行了矿物学分析，并对选定的样品进行了抛光后的立体显微镜研究。王水提取的样品中As为10~168万mg kg−1，铜为12~194m g kg−1，铅为31~308m g kg−1，锌为12 2~1129m g kg−1，各年龄段的差异较大。几乎所有样品中的水溶性铜、铅和锌的含量都低于检测限，这是由于尾矿中的碱性pH值(7.17~8.61)所致。水可萃取态As仅在16a以上的尾矿中检出，浓度在0.06~7.58m g·kg-1·−-1之间。尾矿中与硫化物伴生的Te比例随着年龄的增长而下降，而与铁氧化物伴生的Te比例随着暴露时间的延长而增加，As、Cu、Zn在60年后接近平衡，铅在40年后接近平衡。对抛光样品的观察表明，氧化一直进行到次生矿物的涂层覆盖并保护硫化物矿物颗粒免受进一步风化。一级速率方程被调整为与硫化物或氧化铁缔合的TE的比例。假定硫化物组分中的Te对应于毒砂(FeAsS)、黄铜矿(CuFeS_2)、方铅矿(PbS)和闪锌矿(ZnS)，硫化物的相对氧化速率顺序为：PbS>；ZnS>；FeAsS-≈CuFeS_2，而元素与铁氧化物的相对亲和力顺序为：Cu-≈-Zn>；As>；
We studied the behavior of the trace elements (TE) As, Cu, Pb and Zn associated with sulphide minerals in tailings of different age at the Guanajuato mining district, Mexico. The objective was to determine the dominant fractions into which the TE move as tailings age and to identify how much time is needed until the dominant metal fractions approach equilibrium. We collected 21 samples from the surface of mine waste deposits of different ages (0, 2 , 4, 16, 70, 75, and 100 years), and measured their aqua regia extractable contents of As, Cu, Pb and Zn. We also applied a sequential extraction procedure to quantify water soluble TE as well as TE associated with carbonates, iron oxides, sulphides and the residual fraction. The mineralogy was analysed by X-ray diffraction, and selected samples were studied on polished specimens through a stereoscopic microscope. The TE in samples extracted with aqua regia ranged between 10 and 168 mg kg−1for As, 12 to 194 mg kg−1for Cu, 31 to 308 mg kg−1for Pb, and 122 to 1129 mg kg−1for Zn, and varied in a wide range within each age group of tailings. Water soluble Cu, Pb and Zn contents were below detection limits in almost all samples, which was attributed to the alkaline pH (7.17 to 8.61) in the tailings. Water extractable As was detected only in tailings older than 16 years, and concentrations ranged between 0.06 and 7.58 mg kg−1. The proportion of TE associated with sulphides decreased in the tailings as they age, while the proportion of TE associated with iron oxides increased with time of exposure to the atmosphere, approximating equilibrium after 60 years for As, Cu and Zn, and after 40 years for Pb. Observations of polished specimens suggests that oxidation proceeds until coatings of secondary minerals cover and protect sulphide mineral grains from further weathering. First order rate equations were adjusted to the proportions of TE associated with either sulphides or iron oxides. Assuming that the TE in sulphide fractions correspond to arsenopyrite (FeAsS), chalcopyrite (CuFeS2), galena (PbS) and sphalerite (ZnS), the relative oxidation rate of sulphides followed the order: PbS>ZnS>FeAsS≈CuFeS2, while the relative affinity of the elements with iron oxides followed the sequence Cu≈Zn>As>Pb.